Validation of the supinator fat pad sign in radial head and neck fractures

Objective: To assess the displacement of the supinator fat pad in radial head and neck fractures and to validate its significance. Material and methods: One hundred two adult patients from the Royal Orthopaedic Hospital, Birmingham, United Kingdom and Sultan Qaboos University Hospital, Muscat, Oman with confirmed radial head and/or neck fractures were included. Fractures were classified using the Mason-Johnston classification. The displacement of the supinator fat pad from the radius was measured on anterior-posterior (AP) and lateral radiographs and correlated to fracture classification. Results: The supinator fat pad was on average displaced by 10.6 mm and 13.8 mm from the radius on AP and lateral radiographs, respectively. The displacement of the fat pad progressively increased between non-displaced (Mason I) and severely comminuted (Mason III) fractures on both the AP (10.25 to 14.25 mm) and lateral (12.70 to 16.00 mm) projections. The progression of displacement on AP (p = 0.016) and on lateral (p = 0.007) projections was statistically significant. Fracture dislocation was not associated with increased fat pad displacement. Conclusion: The supinator fat pad sign is a useful adjunct in the assessment of radial head and neck fractures.